[booster] gemini plugin support shard checkpoint (#3610)

* gemini plugin add shard checkpoint save/load

* gemini plugin add shard checkpoint save/load

* gemini plugin add shard checkpoint save/load

* gemini plugin add shard checkpoint save/load

* gemini plugin add shard checkpoint save/load

* gemini plugin add shard checkpoint save/load

* gemini plugin add shard checkpoint save/load

* gemini plugin add shard checkpoint save/load

* gemini plugin add shard checkpoint save/load

* gemini plugin add shard checkpoint save/load

* gemini plugin add shard checkpoint save/load

* gemini plugin add shard checkpoint save/load

* gemini plugin add shard checkpoint save/load

* gemini plugin add shard checkpoint save/load

* gemini plugin support shard checkpoint

* [API Refactoring]gemini plugin support shard checkpoint

* [API Refactoring]gemini plugin support shard checkpoint

* [API Refactoring]gemini plugin support shard checkpoint

* [API Refactoring]gemini plugin support shard checkpoint

* [API Refactoring]gemini plugin support shard checkpoint

* [API Refactoring]gemini plugin support shard checkpoint

* [API Refactoring]gemini plugin support shard checkpoint

* [API Refactoring]gemini plugin support shard checkpoint

* [API Refactoring]gemini plugin support shard checkpoint

* [API Refactoring]gemini plugin support shard checkpoint

* [API Refactoring]gemini plugin support shard checkpoint

* [API Refactoring]gemini plugin support shard checkpoint

* [API Refactoring]gemini plugin support shard checkpoint

---------

Co-authored-by: luchen <luchen@luchendeMBP.lan>
Co-authored-by: luchen <luchen@luchendeMacBook-Pro.local>

colossalai/booster/plugin/gemini_plugin.py

@@ -1,6 +1,9 @@
 import random
 import warnings
 from typing import Callable, List, Optional, Tuple, Union
+from pathlib import Path
+import os
+import logging
 
 import numpy as np
 import torch
@@ -20,6 +23,13 @@ from colossalai.utils import get_current_device
 from colossalai.zero import GeminiDDP, zero_model_wrapper, zero_optim_wrapper
 from colossalai.zero.gemini.memory_tracer import MemStats
 
+from colossalai.checkpoint_io.utils import (
+    get_base_filenames,
+    get_shard_filename
+    )
+
+from colossalai.checkpoint_io import CheckpointIndexFile
+
 from .plugin_base import Plugin
 
 __all__ = ['GeminiPlugin']
@@ -62,6 +72,40 @@ class GeminiCheckpointIO(GeneralCheckpointIO):
         if self.coordinator.is_master():
             super().save_lr_scheduler(lr_scheduler, checkpoint)
 
+    def save_sharded_model(self, model: GeminiDDP, checkpoint_path: str, gather_dtensor: bool = False, variant: Optional[str] = None, max_shard_size: int = 1024, use_safetensors: bool = False):
+        """
+        Save sharded model
+        """
+        state_dict_shard = model.state_dict_shard(max_shard_size=max_shard_size, only_rank_0=True, dtype=torch.float32)
+        weights_name, save_index_file = get_base_filenames(variant, use_safetensors)
+        total_size = 0
+        index_file = CheckpointIndexFile(checkpoint_path)
+        for idx, shard_pair in enumerate(state_dict_shard):
+            if not self.coordinator.is_master():
+                continue
+            shard = shard_pair[0]
+            shard_file = get_shard_filename(weights_name, idx)
+            total_size = total_size + shard_pair[1]
+            for key in shard.keys():
+                index_file.append_weight_map(key, shard_file)
+            
+            checkpoint_file_path = os.path.join(checkpoint_path, shard_file)
+            save_state_dict(shard, checkpoint_file_path, use_safetensors)
+        
+        index_file.append_meta_data("total_size", total_size)
+        index_file.write_index_file(save_index_file)
+        logging.info(
+            f"The model is going to be split to checkpoint shards. "
+            f"You can find where each parameters has been saved in the "
+            f"index located at {save_index_file}."
+        )
+
+
+    def load_sharded_model(self, model: GeminiDDP, checkpoint_index_file: Path, strict: bool = False, use_safetensors: bool = False):
+        """
+        load shard model, load model from multiple files
+        """
+        return super().load_sharded_model(model, checkpoint_index_file, strict, use_safetensors, load_sub_module=False)
 
 class GeminiModel(ModelWrapper):
 

colossalai/checkpoint_io/general_checkpoint_io.py

@@ -1,12 +1,12 @@
 from pathlib import Path
+from functools import reduce
 
 import torch.nn as nn
 from torch.optim import Optimizer
 import logging
 import os
-import json
 import gc
-from typing import Optional
+from typing import Optional, Iterator, OrderedDict, Tuple
 
 from .checkpoint_io_base import CheckpointIO
 from .index_file import CheckpointIndexFile
@@ -18,10 +18,9 @@ from .utils import (
     shard_checkpoint,
     load_shard_state_dict,
     load_state_dict_into_model,
-    add_variant
+    get_shard_filename,
+    get_base_filenames
     )
-from .utils import SAFE_WEIGHTS_NAME, WEIGHTS_NAME, SAFE_WEIGHTS_INDEX_NAME, WEIGHTS_INDEX_NAME
-
 
 __all__ = ['GeneralCheckpointIO']
 
@@ -85,30 +84,32 @@ class GeneralCheckpointIO(CheckpointIO):
         
         # shard checkpoint
         state_dict = model.state_dict()
-        weights_name = SAFE_WEIGHTS_NAME if use_safetensors else WEIGHTS_NAME
+        state_dict_shard = shard_checkpoint(state_dict, max_shard_size=max_shard_size)
-        weights_name = add_variant(weights_name, variant)
+
-        shards, index = shard_checkpoint(state_dict, max_shard_size=max_shard_size, weights_name=weights_name)
+        weights_name, save_index_file = get_base_filenames(variant, use_safetensors)
+        total_size = 0
+        index_file = CheckpointIndexFile(checkpoint_path)
+        for idx, shard_pair in enumerate(state_dict_shard):
+            shard = shard_pair[0]
+            shard_file = get_shard_filename(weights_name, idx)
+            total_size = total_size + shard_pair[1]
+            for key in shard.keys():
+                index_file.append_weight_map(key, shard_file)
             
-        # Save the model
-        for shard_file, shard in shards.items():
             checkpoint_file_path = os.path.join(checkpoint_path, shard_file)
             save_state_dict(shard, checkpoint_file_path, use_safetensors)
         
-        # save index file
+        index_file.append_meta_data("total_size", total_size)
-        save_index_file = SAFE_WEIGHTS_INDEX_NAME if use_safetensors else WEIGHTS_INDEX_NAME
+        index_file.write_index_file(save_index_file)
-
-        save_index_file = os.path.join(checkpoint_path, add_variant(save_index_file, variant))
-        with open(save_index_file, "w", encoding="utf-8") as f:
-            content = json.dumps(index, indent=2, sort_keys=True) + "\n"
-            f.write(content)
         logging.info(
-            f"The model is bigger than the maximum size per checkpoint ({max_shard_size}) and is going to be "
+            f"The model is going to be split to checkpoint shards. "
-            f"split in {len(shards)} checkpoint shards. You can find where each parameters has been saved in the "
+            f"You can find where each parameters has been saved in the "
             f"index located at {save_index_file}."
         )
 
 
-    def load_sharded_model(self, model: nn.Module, checkpoint_index_file: Path, strict: bool = False, use_safetensors: bool = False):
+    def load_sharded_model(self, model: nn.Module, checkpoint_index_file: Path, strict: bool = False, 
+                           use_safetensors: bool = False, load_sub_module: bool = True):
         """
         load shard model, load model from multiple files
         """
@@ -122,17 +123,21 @@ class GeneralCheckpointIO(CheckpointIO):
         # read checkpoint index file
         ckpt_index_file = CheckpointIndexFile.from_file(checkpoint_index_file)
         checkpoint_files, _ = ckpt_index_file.get_checkpoint_fileanames()
-        missing_keys = ckpt_index_file.get_all_param_names()
+        missing_keys = []
 
         for shard_file in checkpoint_files:
             state_dict = load_shard_state_dict(Path(shard_file), use_safetensors)
-            load_state_dict_into_model(model, state_dict, missing_keys, strict)
+            load_state_dict_into_model(model, state_dict, missing_keys, strict, load_sub_module)
             del state_dict
             gc.collect()
 
-        if strict and len(missing_keys) > 0:
+        if strict:
-            error_msgs = 'Missing key(s) in state_dict: {}. '.format(
+            remain_keys = reduce(lambda a, b: a & b, map(set, missing_keys))
-                        ', '.join('"{}"'.format(k) for k in missing_keys))
+            if len(remain_keys) > 0:
-            raise RuntimeError('Error(s) in loading state_dict for {}:\n\t{}'.format(
+                error_msgs = 'Missing key(s) in state_dict: {}. '.format(
-                               self.__class__.__name__, "\n\t".join(error_msgs)))
+                            ', '.join('"{}"'.format(k) for k in missing_keys))
+                raise RuntimeError('Error(s) in loading state_dict for {}:\n\t{}'.format(
+                                self.__class__.__name__, "\n\t".join(error_msgs)))
+
+
 

colossalai/checkpoint_io/index_file.py

@@ -1,6 +1,8 @@
 import json
 from pathlib import Path
 from typing import Any, List, Union
+import os
+import json
 
 from .utils import is_dtensor_checkpoint
 
@@ -18,8 +20,8 @@ class CheckpointIndexFile:
         >>> index.export('new_index.json')
     """
 
-    def __init__(self) -> None:
+    def __init__(self, root_path=None) -> None:
-        self.root_path = None
+        self.root_path = root_path
         self.metadata: dict = dict()
         self.weight_map: dict = dict()
 
@@ -154,3 +156,13 @@ class CheckpointIndexFile:
         Get all the weight keys.
         """
         return list(self.weight_map.keys())
+    
+    def write_index_file(self, save_index_file):
+        """
+        Wriete index file.
+        """
+        save_index_file = os.path.join(self.root_path, save_index_file)
+        index = {"metadata": self.metadata, "weight_map": self.weight_map}
+        with open(save_index_file, "w", encoding="utf-8") as f:
+            content = json.dumps(index, indent=2, sort_keys=True) + "\n"
+            f.write(content)

colossalai/checkpoint_io/utils.py

@@ -2,7 +2,7 @@
 from pathlib import Path
 import torch
 import torch.nn as nn
-from typing import List, Dict, Mapping, OrderedDict, Optional, Tuple
+from typing import List, Mapping, OrderedDict, Optional, Tuple, Iterator
 from colossalai.tensor.d_tensor.d_tensor import DTensor
 import re
 
@@ -77,55 +77,35 @@ def is_safetensor_checkpoint(checkpoint_file_path: str) -> bool:
 # ======================================
 # Helper functions for saving shard file
 # ======================================
-def shard_checkpoint(state_dict: torch.Tensor, max_shard_size: int = 1024, weights_name: str = WEIGHTS_NAME):
+def shard_checkpoint(state_dict: torch.Tensor, max_shard_size: int = 1024) -> Iterator[Tuple[OrderedDict, int]]:
  
     """
     Splits a model state dictionary in sub-checkpoints so that the final size of each sub-checkpoint does not exceed a
     given size.
     """
-    sharded_state_dicts = []
     current_block = {}
     current_block_size = 0
-    total_size = 0
 
     for key, weight in state_dict.items():
+        ret_block = None
+        ret_block_size = 0
         if type(weight) != DTensor:
             weight_size = calculate_tensor_size(weight)
 
             # If this weight is going to tip up over the maximal size, we split.
             if current_block_size + weight_size > max_shard_size:
-                sharded_state_dicts.append(current_block)
+                ret_block = current_block
+                ret_block_size = current_block_size
                 current_block = {}
                 current_block_size = 0
-
             current_block[key] = weight
             current_block_size += weight_size
-            total_size += weight_size
             
-    # Add the last block
+        if ret_block != None:
-    sharded_state_dicts.append(current_block)
+            yield ret_block, ret_block_size
 
-    # If we only have one shard, we return it
+    yield current_block, current_block_size
-    if len(sharded_state_dicts) == 1:
-        return {weights_name: sharded_state_dicts[0]}, None
 
-    # Otherwise, let's build the index
-    weight_map = {}
-    shards = {}
-
-    for idx, shard in enumerate(sharded_state_dicts):
-        shard_file = weights_name.replace(".bin", f"-{idx+1:05d}-of-{len(sharded_state_dicts):05d}.bin")
-        shard_file = shard_file.replace(
-            ".safetensors", f"-{idx + 1:05d}-of-{len(sharded_state_dicts):05d}.safetensors"
-        )
-        shards[shard_file] = shard
-        for key in shard.keys():
-            weight_map[key] = shard_file
-
-    # Add the metadata
-    metadata = {"total_size": total_size}
-    index = {"metadata": metadata, "weight_map": weight_map}
-    return shards, index
 
 def load_shard_state_dict(checkpoint_file: Path, use_safetensors: bool =False):
     """
@@ -146,7 +126,7 @@ def load_shard_state_dict(checkpoint_file: Path, use_safetensors: bool =False):
     else:
         return torch.load(checkpoint_file)
     
-def load_state_dict_into_model(model: nn.Module, state_dict: torch.Tensor, missing_keys: List, strict: bool = False):
+def load_state_dict_into_model(model: nn.Module, state_dict: torch.Tensor, missing_keys: List, strict: bool = False, load_sub_module: bool = True):
     r"""Copies parameters and buffers from :attr:`state_dict` into
     this module and its descendants. 
 
@@ -167,29 +147,22 @@ def load_state_dict_into_model(model: nn.Module, state_dict: torch.Tensor, missi
     if metadata is not None:
         state_dict._metadata = metadata
 
-    def load(module: nn.Module, state_dict, prefix=""):
+    def load(module: nn.Module, state_dict, prefix="", load_sub_module: bool = True):
         local_metadata = {} if metadata is None else metadata.get(prefix[:-1], {})
-        args = (state_dict, prefix, local_metadata, True, [], [], error_msgs)
+        args = (state_dict, prefix, local_metadata, True, sub_missing_keys, [], error_msgs)
         # Parameters of module and children will start with prefix. We can exit early if there are none in this
         # state_dict
         if len([key for key in state_dict if key.startswith(prefix)]) > 0:
             module._load_from_state_dict(*args)
+        if load_sub_module:
+            for name, child in module._modules.items():
+                if child is not None:
+                    load(child, state_dict, prefix + name + ".")
 
-        for name, child in module._modules.items():
+    load(model, state_dict, "", load_sub_module)
-            if child is not None:
-                load(child, state_dict, prefix + name + ".")
-
-    load(model, state_dict, "")
     del load
 
-    # deal with missing key
+    missing_keys = missing_keys.append(sub_missing_keys)
-    if len(missing_keys) > 0:
-        deleted_keys = []
-        for key in missing_keys:
-            if key not in sub_missing_keys:
-                deleted_keys.append(key)
-        for key in deleted_keys:
-            missing_keys.remove(key)
 
     if strict:
         if len(unexpected_keys) > 0:
@@ -417,3 +390,24 @@ def add_variant(weights_name: str, variant: Optional[str] = None) -> str:
         weights_name = ".".join(splits)
 
     return weights_name
+
+
+def get_base_filenames(variant: str=None, use_safetensors: bool=False):
+        """
+        generate base weight filenames
+        """
+        weights_name = SAFE_WEIGHTS_NAME if use_safetensors else WEIGHTS_NAME
+        weights_name = add_variant(weights_name, variant)
+
+        save_index_file = SAFE_WEIGHTS_INDEX_NAME if use_safetensors else WEIGHTS_INDEX_NAME
+        save_index_file = add_variant(save_index_file, variant)
+
+        return weights_name, save_index_file
+
+def get_shard_filename(weights_name: str, idx: int):
+    """
+    get shard file name
+    """
+    shard_file = weights_name.replace(".bin", f"-{idx+1:05d}.bin")
+    shard_file = shard_file.replace(".safetensors", f"-{idx + 1:05d}.safetensors")
+    return shard_file

colossalai/zero/gemini/gemini_ddp.py

@@ -2,7 +2,7 @@ import itertools
 from collections import OrderedDict
 from contextlib import nullcontext
 from functools import partial
-from typing import Dict, Iterator, List, Optional, Union
+from typing import Dict, Iterator, List, Optional, Union, Tuple, Set
 
 import torch
 import torch.distributed as dist
@@ -96,8 +96,35 @@ class ZeroDDP(ColoDDP):
                 param_name = m_name + '.' + p_name if m_name else p_name
                 self.name2param[param_name] = p_var
         super().__init__(module, process_group=ColoProcessGroup())
+        self._non_persistent_buffers_set=self._get_non_persistent_buffers_set(module)
         self._cast_buffers()
 
+    def _get_non_persistent_buffers_set(self, module, memo: Optional[Set[nn.Module]] = None, prefix: str = '', remove_duplicate: bool = True):
+
+            r"""
+            Args:
+                memo: a memo to store the set of modules already added to the result
+                prefix: a prefix that will be added to the name of the module
+                remove_duplicate: whether to remove the duplicated module instances in the result
+                    or not
+            """
+
+            if memo is None:
+                memo = set()
+            self_non_persistent_set = set()
+            if module not in memo:
+                if remove_duplicate:
+                    memo.add(module)
+                self_non_persistent_set = set(map(lambda key: prefix + ('.' if prefix else '') + key, module._non_persistent_buffers_set))
+                for name, sub_module in module._modules.items():
+                    if sub_module is None:
+                        continue
+                    submodule_prefix = prefix + ('.' if prefix else '') + name
+                    child_non_persistent_set = self._get_non_persistent_buffers_set(sub_module, memo, submodule_prefix, remove_duplicate)
+                    self_non_persistent_set = set.union(self_non_persistent_set, child_non_persistent_set)
+            return self_non_persistent_set
+    
+
     def _post_forward(self):
         """This function is only triggered for inference.
         """
@@ -604,7 +631,7 @@ class ZeroDDP(ColoDDP):
                          keep_vars: bool = False,
                          max_shard_size: int = 1024,
                          only_rank_0: bool = True,
-                         dtype: torch.dtype = torch.float16) -> Iterator[OrderedDict]:
+                         dtype: torch.dtype = torch.float16) -> Iterator[Tuple[OrderedDict, int]]:
         """Returns dictionaries containing a whole state of the module one by one. The max size of dictionary shard is specified by ``max_shard_size``.
 
         Both parameters and persistent buffers (e.g. running averages) are included.
@@ -644,9 +671,9 @@ class ZeroDDP(ColoDDP):
                         gathered_param_buffer.update(self._get_chunk_to_save_data(chunk, only_rank_0, dtype))
                     gathered_param = gathered_param_buffer.pop(fp32_param)
 
-                block = sharder.append(prefix + name, gathered_param)
+                block, block_size = sharder.append(prefix + name, gathered_param)
                 if block is not None:
-                    yield block
+                    yield block, block_size
 
         del fp16_to_fp32
         del gathered_param_buffer
@@ -655,19 +682,19 @@ class ZeroDDP(ColoDDP):
         for name, buf in self.named_buffers():
             if buf is not None and name not in self._non_persistent_buffers_set:
                 buffer = buf if keep_vars else buf.detach()
-                block = sharder.append(prefix + name, buffer)
+                block, block_size = sharder.append(prefix + name, buffer)
                 if block is not None:
-                    yield block
+                    yield block, block_size
         # save extra states
         extra_state_key = prefix + _EXTRA_STATE_KEY_SUFFIX
         if getattr(self.__class__, "get_extra_state",
                    torch.nn.Module.get_extra_state) is not torch.nn.Module.get_extra_state:
             extra_state = self.get_extra_state()
-            block = sharder.append(extra_state_key, extra_state)
+            block, block_size = sharder.append(extra_state_key, extra_state)
             if block is not None:
-                yield block
+                yield block, block_size
 
-        yield sharder.current_block
+        yield sharder.current_block, sharder.current_block_size
 
 
 class _StateDictSharder:
@@ -677,16 +704,18 @@ class _StateDictSharder:
         self.current_block = OrderedDict()
         self.current_block_size = 0
 
-    def append(self, name: str, tensor: torch.Tensor) -> Optional[OrderedDict]:
+    def append(self, name: str, tensor: torch.Tensor) -> Tuple[Optional[OrderedDict], int]:
         tensor_size = calculate_tensor_size(tensor)
         ret_block = None
+        ret_block_size = 0
         if self.current_block_size + tensor_size > self.max_shard_size:
             ret_block = self.current_block
+            ret_block_size = self.current_block_size
             self.current_block = OrderedDict()
             self.current_block_size = 0
         self.current_block[name] = tensor
         self.current_block_size += tensor_size
-        return ret_block
+        return ret_block, ret_block_size
 
 
 class GeminiDDP(ZeroDDP):

tests/test_checkpoint_io/test_general_checkpoint_io.py

@@ -1,16 +1,21 @@
 import tempfile
 import pytest
 import torch
-import logging
 from torch.optim import Adam
 from torchvision.models import resnet18
-from pathlib import Path
-import os
-import subprocess
 
 from colossalai.checkpoint_io import GeneralCheckpointIO
+from colossalai.booster.plugin.gemini_plugin import GeminiCheckpointIO
 from colossalai.testing import clear_cache_before_run, parameterize
 
+import colossalai
+from colossalai.testing import parameterize, rerun_if_address_is_in_use, spawn
+from colossalai.utils.cuda import get_current_device
+from colossalai.zero import ColoInitContext, ZeroDDP
+from colossalai.zero.gemini.chunk import ChunkManager, search_chunk_configuration
+from colossalai.zero.gemini.gemini_mgr import GeminiManager
+from tests.components_to_test.registry import non_distributed_component_funcs
+
 # ========
 # Note:
 # 1. due to checkpoint IO can be quite slow if tested with all models, we will only test on resnet for now
@@ -83,7 +88,6 @@ def test_sharded_checkpoint(use_safetensors: bool):
         suffix = ".bin"
         WEIGHTS_INDEX_NAME = "model.bin.index.json"
     
-    # model_ckpt_dir = tempfile.TemporaryDirectory(suffix=suffix)
     model_ckpt_dir = tempfile.TemporaryDirectory()
     optimizer_ckpt_tempfile = tempfile.NamedTemporaryFile()
 
@@ -104,6 +108,87 @@ def test_sharded_checkpoint(use_safetensors: bool):
     recursive_check(model.state_dict(), new_model.state_dict())
     recursive_check(optimizer.state_dict(), new_optimizer.state_dict())
 
+@parameterize('placement_policy', ['cuda', 'cpu'])
+@parameterize('model_name', ['bert'])
+@parameterize('use_safetensors', [True, False])
+def hf_load_colossalai_checkpoint(placement_policy, model_name, use_safetensors: bool):
+    from transformers import BertTokenizer, BertModel, BertForMaskedLM, BertConfig, BertForSequenceClassification
+
+    model_ckpt_dir = tempfile.TemporaryDirectory()
+    get_components_func = non_distributed_component_funcs.get_callable(model_name)
+    model_builder, *_ = get_components_func()
+
+    with ColoInitContext(device=get_current_device()):
+        bert_model = model_builder()
+    bert_model.config.save_pretrained(save_directory=model_ckpt_dir.name)
+    config_dict, *_ = search_chunk_configuration(bert_model, search_range_mb=1, search_interval_byte=100)
+    chunk_manager = ChunkManager(config_dict)
+    gemini_manager = GeminiManager(placement_policy, chunk_manager)
+    bert_model = ZeroDDP(bert_model, gemini_manager)
+    bert_model.train()
+
+    ckpt_io = GeminiCheckpointIO()
+    if ckpt_io.coordinator.is_master():
+        model_size = sum(p.numel() * p.element_size() for p in bert_model.parameters()) / 1024**2
+        ckpt_io.save_model(bert_model, model_ckpt_dir.name, True, True, "", (model_size / 3), use_safetensors=use_safetensors)
+        new_bert_model = BertForSequenceClassification.from_pretrained(model_ckpt_dir.name)
+        recursive_check(bert_model.state_dict(only_rank_0=True, dtype=torch.float32), new_bert_model.state_dict())
+    
+    model_ckpt_dir.cleanup()
+        
+
+
+@parameterize('placement_policy', ['cuda', 'cpu'])
+@parameterize('model_name', ['gpt2', 'bert'])
+@parameterize('use_safetensors', [True, False])
+def exam_state_dict(placement_policy, model_name: str, use_safetensors: bool):
+    get_components_func = non_distributed_component_funcs.get_callable(model_name)
+    model_builder, *_ = get_components_func()
+
+    with ColoInitContext(device=get_current_device()):
+        model = model_builder()
+        new_model = model_builder()
+
+    config_dict, *_ = search_chunk_configuration(model, search_range_mb=1, search_interval_byte=100)
+    chunk_manager = ChunkManager(config_dict)
+    gemini_manager = GeminiManager(placement_policy, chunk_manager)
+    model = ZeroDDP(model, gemini_manager)
+    model.train()
+
+    new_config_dict, *_ = search_chunk_configuration(new_model, search_range_mb=1, search_interval_byte=100)
+    new_chunk_manager = ChunkManager(new_config_dict)
+    new_gemini_manager = GeminiManager(placement_policy, new_chunk_manager)
+    new_model = ZeroDDP(new_model, new_gemini_manager)
+
+    model_ckpt_dir = tempfile.TemporaryDirectory()
+
+    ckpt_io = GeminiCheckpointIO()
+    model_size = sum(p.numel() * p.element_size() for p in model.parameters()) / 1024**2
+    ckpt_io.save_model(model, model_ckpt_dir.name, True, True, "epoch", (model_size / 3), use_safetensors=use_safetensors)
+
+    # load model
+    if ckpt_io.coordinator.is_master():
+        ckpt_io.load_model(new_model, model_ckpt_dir.name, strict=True)
+        model_dict = model.state_dict(only_rank_0=True)
+        new_model_dict = new_model.state_dict(only_rank_0=True)
+        recursive_check(model_dict, new_model_dict)
+
+    model_ckpt_dir.cleanup()
+
+
+def run_dist(rank, world_size, port):
+    config = {}
+    colossalai.launch(config=config, rank=rank, world_size=world_size, host='localhost', port=port, backend='nccl')
+    exam_state_dict()
+    hf_load_colossalai_checkpoint()
+
+
+@pytest.mark.dist
+@pytest.mark.parametrize('world_size', [4, 4])
+@rerun_if_address_is_in_use()
+def test_gemini_ckpIO(world_size):
+    spawn(run_dist, world_size)
+
 
 # do recursive check for the optimizer state dict
 # if the value is a dict, compare its values
@@ -117,10 +202,14 @@ def recursive_check(d1, d2):
         elif isinstance(v, list):
             for i in range(len(v)):
                 if isinstance(v[i], torch.Tensor):
+                    v[i] = v[i].to("cpu")
+                    d2[k][i] = d2[k][i].to("cpu")
                     assert torch.equal(v[i], d2[k][i])
                 else:
                     assert v[i] == d2[k][i]
         elif isinstance(v, torch.Tensor):
+            v = v.to("cpu")
+            d2[k] = d2[k].to("cpu")
             assert torch.equal(v, d2[k])
         else:
             assert v == d2[k]

tests/test_zero/test_gemini/test_zeroddp_state_dict_shard.py

@@ -31,14 +31,13 @@ def exam_state_dict(placement_policy, model_name: str):
     zero_dict = model.state_dict(only_rank_0=False)
     accumulated_keys = set()
     # ensure number of shards > 1
-    for shard in model.state_dict_shard(max_shard_size=(model_size / 3), only_rank_0=False):
+    for shard, _ in model.state_dict_shard(max_shard_size=(model_size / 3), only_rank_0=False):
         for key, value in shard.items():
             assert key not in accumulated_keys, f"key `{key}` is duplicated."
             accumulated_keys.add(key)
             assert key in zero_dict, f"{key} not in ZeRO dictionary."
             assert torch.equal(value, zero_dict[key]), f"{key} not equal."
 
-
 def run_dist(rank, world_size, port):
     config = {}
     colossalai.launch(config=config, rank=rank, world_size=world_size, host='localhost', port=port, backend='nccl')